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Our Sun

All the planets, moons, and smaller things in the solar system are just dust, compared to the star that they orbit; the Sun contains 99.9% of the mass of the solar system. We think of it as our source of light, but it doesn't just emit photons. The solar wind blasts fast-moving electrons, protons, and highly ionized atoms in all directions, a constant stream punctuated by ferocious coronal mass ejections. The solar wind carries with it a magnetic field wound into a tight spiral by the Sun's rotation.

The solar wind pushes outward against the interstellar medium, penning the solar system inside a bubble called the "heliosphere" that's at least 200 AU across. The twin Voyager spacecraft are now probing the heliosphere's edges. Closer to home, a fleet of spacecraft monitors the space weather generated by the Sun, warning us of its effects on Earth, from the benevolent (aurorae) to the potentially disastrous (irradiation of astronauts and damage to communications satellites and power grids).  Currently operating solar space observatories include ACE, GGS, WIND, Hinode, PICARD, RHESSI, SOHO, SDO, Solar Monitoring Observatory, and STEREO.

Latest Blog Entries about the Sun, Heliosphere, and Space Weather

Yet more planet transits

Posted by Emily Lakdawalla on 2012/06/14 11:00 CDT | 7 comments

A reader comment on Jay Pasachoff's post last week about Venus transits viewed from other planets had me asking whether transits of other planets were also interesting to astronomers. Jay provided some answers!

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Video: Comet Lovejoy entered SOHO's LASCO C3 field of view this morning!

Posted by Emily Lakdawalla on 2011/12/14 09:37 CST

An animation of comet Lovejoy entering the field of view of one of SOHO's Sun-monitoring cameras.

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Transit of Venus June 5: Why Should You Care and How to Observe

Posted by Bruce Betts on 2012/06/02 01:56 CDT | 2 comments

A rare astronomical event occurs June 5/6. Find out why you should care and how to observe it.

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The scale of our solar system

Posted by Emily Lakdawalla on 2011/05/02 11:26 CDT

Space.com has taken advantage of the infinitely scrollable nature of Web pages to produce a really cool infographic on the scales of orbital distances in the solar system.

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The Mercury Transit You Probably Missed

Posted by Karl Battams on 2013/12/30 10:29 CST | 2 comments

Planetary transits of the Sun by Mercury and Venus don't come along very often, and when they do we make a big deal of it because, well, it's really cool!

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